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Police said an unattended toddler climbed into a hot car and became trapped inside, later dying at the hospital. Kate Larsen reports from Sylmar for the NBC4 News at 11 on Wednesday, July 30, 2014. (Published Thursday, July 31, 2014)

A 3-year-old boy died Wednesday after becoming trapped in a hot car in Sylmar, police said.

Officers were called about 3:30 p.m. to a home in the 14400 block of West Foothill Boulevard, where the child had climbed into a Toyota Camry and was unable to get out, the Los Angeles Police Department said.

The child was taken to a hospital in grave condition, police said. He was later pronounced dead.

Investigators believe the child was playing outside while his parents and 14-year-old brother were napping inside. Police say the boy's parents told detectives they all took a nap around noon.

It was unclear how the child became locked inside the car. Investigators said the father found him around 3 p.m. in the car parked in the family's front yard and called 911.

It was 88 degrees in Sylmar at noon and 98 degrees by 3 p.m. In a car with the windows up, the temperature is exponentially higher.

No arrests have been made in connection with the boy's death, police said.

"Our investigation will determine if this was an accident or something worse, all we have to go on right now are the statements from the parents," LAPD Lt. Paul Vernon said.

Police said they were interviewing the parents at a relative's home Wednesday night. For now, investigators are treating this incident as an accident and awaiting the coroner's autopsy report to determine the exact cause of death.

"They had several kids running around the yard, they were really nice people and seemed to be really good with their kids," neighbor Kim Kesley said.